Subcutaneous injection is a means of administering therapeutics that requires proper placement of the injection needle. The therapeutic needs to be injected beneath the skin but not into the underlying muscle tissue. The injection site is a substantial factor in controlling the rate of systemic disbursement of the therapeutic and the dosage regimens of a significant number of therapeutics are keyed to their administration to subcutaneous tissue.
The proper placement of the injection needle is typically achieved by controlling the depth of its penetration beneath the skin and this in turn can be controlled by how far the needle is advanced into and through the skin and the angle between the needle and the skin. One approach has been to pinch the skin and underlying subcutaneous tissue and insert the injection needle into the gathered tissue. However, this approach requires the use of two hands. It also limits the injection sites to those where there is adequate tissue to be pinched.
Commonly the injection needle is fitted to a syringe and the syringe is used to direct the placement of the injection needle. The proper placement of the injection needle with this mechanical arrangement can require considerable manual dexterity and may be particularly difficult in circumstances in which there is movement of the patient or the syringe, for instance when administration is attempted on a moving conveyance like a car or train.
Typically the faster the injection needle is inserted into the tissue the less pain that is experienced. However, the insertion may be slower than optimum because of the mechanical arrangement. The insertion may proceed slowly out of a concern to achieve proper positioning of the injection needle.
Some discomfort may be experienced if the injection needle moves after insertion and before the therapeutic is fully dispersed. The mechanical arrangement of the syringe located at a considerable distance from the end of the insertion needle being the sole means of controlling the ends location, enhances the probability of such movement and resultant discomfort. This in turn may cause a premature withdrawal of the injection needle before the therapeutic is fully administered.